220 ARCADiE. 



N. kadiata, Hanley. 



Elongated-trigonal, with rufous rays ; epidermis but slightly 

 glossy ; hinder extremity tapering, its dorsal area not sculptured ; 

 inner margin crenated. 



Plate XLVII. fig. 4, 5, and XLVIII. fig. 7. 



Area nucleus, Pulteney, Hutchins, Hist. Dorset, p. 35. — Maton and Rack. 



Dorset Catalog, p. 37. — Turton, Conch. Diction, p. 8, f. 1, 2. 

 Xiicula nucleus, Turt. Dithyra Brit. p. 176, pi. 13, f. 4. — Brit. Marine Conch, 

 p. 105, f. 74. — Macgilliv. Moll. Aberdeenshire, p. 243. 

 „ nucha, Fleming, Brit. Anim. p. 401. 



„ margaritacca, Blainville, Manuel' de Malacologie, pi. 65, f. 5 (not 

 well).— Sowerby, Conch. Manual, f. 137. 



This elegant Nucula is almost exactly the shape of an 

 elongated nitida, that is to say, far more triangular in 

 contour, and far more attenuated posteriorly than in 

 nucleus. Its valves are strong and are more compressed 

 than in either of the shells referred to. From the former of 

 them its scarcely glossy epidermis (the olivaceous hue of 

 which is modified in different individuals by tints of yellow- 

 brown or even green), from the latter the chestnut rays 

 which adorn the exterior and vary as to width and 

 number (sometimes there are additional radiating lines of an 

 iron-grey, and occasionally these alone are present) effec- 

 tually distinguish it. In all stages of growth it preserves 

 its peculiar distinctive features. The swell of the ventral 

 margin is more gradual than in nucleus, its posterior dorsal 

 slope more considerable ; its internal nacre of a less blue 

 cast and rather more iridescent, and its teeth are in general 

 not quite so elongated. In other respects our description 

 of nucleus is equally applicable to the present species. It 

 exceeds that shell however in dimensions, as it attains to 

 at least five-eighths of an inch in length, and nearly half an 



